GfsInitFraction

From Gerris

GfsInitFraction is used to initialise a volume-fraction field from a given surface (typically the shape of an interface to be represented using a Volume-Of-Fluid formulation).

The syntax in parameter files is:

[ GfsGenericInit ] V [ GfsSurface ]

where V is a GfsVariable.

If GfsSurface is defined implicitly, by convention the volume fraction of cells not cut by the interface is set to one if the implicit function is positive and zero otherwise.

Examples

• Rayleigh-Taylor instability

  InitFraction {} T (0.05*cos (2.*M_PI*x) + y) { ty = 0.5 }

• Collapse of a column of grains

    InitFraction Ti ({
	    double diametre = 5e-3;
	    double r0 = 0.677/6.26;
	    double centre = x - 4.*diametre/r0;
	    double top = y - H0 + 9.*diametre/r0;
	    double side = x - R0 + 5.*diametre/r0;
	    return union (union (-top, -side), centre);
    })

    InitFraction T (union(H0 - y, R0 - x))

• Savart--Plateau--Rayleigh instability of a water column

    InitFraction {} T ({
	    x -= 0.5; 
	    y += 0.5; z += 0.5;
	    double r = RADIUS*(1. + EPSILON*cos(M_PI*x));
	    return r*r - y*y - z*z;
    })

• Atomisation of a pulsed liquid jet

    InitFraction T0 (radius*radius - R2(y,z))

• Air-water flow around a Series 60 cargo ship

    InitFraction T (1e-4 - z)

• Time-reversed VOF advection in a shear flow

    InitFraction T (ellipse (0, -.236338, 0.2, 0.2))

    InitFraction { start = end } Tref (ellipse (0, -.236338, 0.2, 0.2))

• Time-reversed advection of a VOF concentration

    InitFraction T CIRCLE

    InitFraction { start = end } Tref CIRCLE

• Time-reversed advection with curvature-based refinement

    InitFraction T (ellipse (0, -.236338, 0.2, 0.2))

    InitFraction { start = end } Tref (ellipse (0, -.236338, 0.2, 0.2))

• Rotation of a straight interface

    InitFraction T (x - 1e-9)

    InitFraction { istep = 1 } Tref (x - t*y)

• Comparison between explicit and implicit diffusion schemes on concentration tracer

    InitFraction T (-difference(sphere(0,0,0,0.4),sphere(0,0,0,0.1)))

• Conservation of diffusive tracer

    InitFraction T (0.01 - (x*x + y*y + z*z))

    InitFraction Te (0.01 - (x*x + y*y + z*z))

• Flow created by a cylindrical volume source

    InitFraction F (R0*R0 - x*x - y*y)

• Mass conservation

    InitFraction T (- ellipse (0, 0.3, 0.1, 0.1))

    InitFraction T1 (- ellipse (0, 0.3, 0.1, 0.1))

• Mass conservation with solid boundary

    InitFraction T (- ellipse (-0.2, 0., 0.05, 0.05))

    InitFraction T1 (- ellipse (-0.2, 0., 0.05, 0.05))

• Momentum conservation for large density ratios

    InitFraction T (- ellipse(-0.3,0,radius,radius))

• Circular droplet in equilibrium

  InitFraction T CIRCLE

• Axisymmetric spherical droplet in equilibrium

  InitFraction T CIRCLE

• Planar capillary waves

  InitFraction T (y - 0.01*cos (2.*M_PI*x))

• Air-Water capillary wave

  InitFraction T (y - 0.01*cos (2.*M_PI*x))

• Fluids of different densities

  InitFraction T (y - 0.01*cos (2.*M_PI*x))

• Pure gravity wave

  InitFraction {} T (y - 0.01*cos (2.*M_PI*x))

• Shape oscillation of an inviscid droplet

    InitFraction T ({ x += 0.5; y += 0.5; return x*x + y*y - RADIUS(x,y)*RADIUS(x,y); })

• Height-Function on parallel subdomains

    InitFraction T (ellipse (0, 0, 0.2, 0.3))

• Scalings for Plateau--Rayleigh pinchoff

   InitFraction T (0.2*(1. + 0.1*sin(M_PI*x)) - y)

• Sessile drop

    InitFraction T (- ellipse (0, 0, 0.3, 0.3))

• Circular dam break on a sphere

    InitFraction P (0.2 - acos(cos(x*M_PI/180.)*cos(y*M_PI/180.)))

• Circular dam break on a rotating sphere

    InitFraction P (0.2 - acos(cos(x*M_PI/180.)*cos(y*M_PI/180.)))

• Circular dam break on a ``cubed sphere''

    InitFraction P (0.2 - acos(cos(x*M_PI/180.)*cos(y*M_PI/180.)))

• Dielectric-dieletric planar balance

    InitFraction T (-y)

• Balance with solid boundaries

    InitFraction T (-y)

• Charge relaxation in an axisymmetric insulated conducting column

    InitFraction T (R0 - y)

• Charge relaxation in a planar cross-section

    InitFraction T (R0*R0 - y*y - x*x)

• Equilibrium of a droplet suspended in an electric field

    InitFraction T (R0*R0 - (x*x + y*y))